A Study to Evaluate the Effect of Mechanical Ventilation on the Inferior Vena Cava Collapsibility Index (IVCCI)

• Determine the inter-rater reliability in obtaining inferior vena cava collapsibility index ultrasound images. [ Time Frame: 24 months ] [ Designated as safety issue: No ]
• Determine the relationship between central venous pressure and inferior vena cava collapsibility index at varying levels of mean airway pressure (MAP). [ Time Frame: 24 Months ] [ Designated as safety issue: No ]

• Determine the inter-rater reliability in obtaining IVCCI ultrasound images. [ Time Frame: 24 months ] [ Designated as safety issue: No ]
• Determine the relationship between CVP and IVCCI at varying levels of mean airway pressure (MAP). [ Time Frame: 24 Months ] [ Designated as safety issue: No ]

Previous research has shown that the Inferior Vena Cava Collapsibility Index (IVCCI) can be used to assess volume status. One limitation of the previous work is that changes in intra-thoracic pressure can influence this measurement, and the magnitude of this effect has never been described. The investigators aim is to correlate the degree of change in IVCCI with the set degree of change in intra-thoracic pressure in a heterogeneous population of critically ill patients.

Initially eligible patients will be those admitted to the OSU MICU and 8ICU within the prior 48 hours. These patients will be screened for predetermined exclusion criteria. Eligible patients will have their IVCCI measured and baseline peak and plateau pressures noted. For those patients meeting a second set of criteria, a common ventilator maneuver will be preformed. The positive end-expiratory pressure will be increased by 5-10 cm/H20 pressure. This procedure will be aborted if ANY safety criteria are exceeded. During the interval, the IVCCI will be re-measured, the ventilator settings will be recorded, and the ventilator will be return to the initial settings. Since changes of these same magnitude are made daily in clinical practice, the risks to the patients in this study will be minimal and no more than that experienced in the course of usual care.

InpatientSample

• Bedside ultrasound only
  Bedside ultrasound to determine the dimensions of the inferior vena cava
• Ultrasound with ventilator changes
  Bedside ultrasound to determine the dimensions of the inferior vena cava pre and post ventilator changes.

Inclusion Criteria:

1. Age>17 years
2. Current use of mechanical ventilation through an endotracheal tube.
3. Admitted to ICU within last 48 hours

Exclusion Criteria:

1. Severe COPD by history (documented FEV1<50% predicted or CT evidence of emphysema)
2. Current suspected Asthma Exacerbation
3. Profound Hypoxia defined as a FiO2 requirement >90% or a PEEP >10 mmHg
4. Patient-ventilator desynchrony or active agitation
5. Unstable O2 requirement as determined by the primary clinical team.
6. Prisoners
7. Bedside clinician refusal (physician or treating nurse).

Exclusion Criteria for ventilator changes:

1. Cardiovascular instability (any increase in rate of vasopressors or i.v. fluid bolus for hypotension within the last four hours)
2. Current PEEP requirements of >15cmH2O
3. Current SpO2 of <88%.